1. Field of the Invention
The present invention relates to the field of combustion technology. It concerns a fuel lance for liquid and/or gaseous fuels for use in a combustion chamber, such as is used in gas turbines for example.
2. Discussion of Background
Fuel lances are used for the injection of liquid and/or gaseous fuels into the combustion chamber of a premixing burner and these fuel lances protrude into the combustion chamber and introduce the fuel or fuels in a suitable distribution into the combustion air which is flowing past.
In the design of such fuel lances, various requirements have to be satisfied and these are provided partly by the environmental conditions and partly by the demands made on them:
The combustion air flowing past the fuel lance has a temperature which is substantially independent of the flow of fuel in the lance. It can be necessary to protect the lance itself, and also the fuels carried in it, from an excessively high combustion air temperature. PA1 If the combustion chamber has to be operated with a high fuel quantity ratio between full load and part load, care must be taken to ensure that the fuel is present with a suitable distribution under every operating condition and can be introduced and mixed in the same manner into the flow of combustion air. Because the aerodynamics of the burner are practically independent of the fuel, the attainment of optimum combustion demands that the gaseous fuel and the liquid fuel should be injected in the same manner into the flow of the combustion air. PA1 To keep the efficiency of the burner as high as possible, as little carrier or auxiliary air as possible should be used in the lance. PA1 Furthermore, it is necessary to ensure that, as far as possible, no recirculation zones or wakes, which are filled with gas containing fuel and can lead to flash-back or thermo-acoustic vibrations, are formed in the region of the fuel lance. PA1 In the injection of liquid fuel, i.e. oil in particular, it is necessary to avoid the finely divided oil/air mixture igniting prematurely. PA1 In the case of liquid fuels, it is also necessary to avoid the formation of troublesome deposits within the lance owing to increased temperatures and evaporation of the fuel since this could impair the operation of the lance in the long term or make it quite impossible. PA1 (a) a liquid fuel pipe extending along a lance center line and surrounding a liquid fuel passage for carrying a liquid fuel; PA1 (b) a gas pipe surrounding the liquid fuel pipe and forming a gas passage between itself and the liquid fuel pipe for carrying a gaseous fuel; PA1 (c) a lance outer shell surrounding the gas pipe and forming an air passage between itself and the gas pipe for carrying cooling air and atomizer air; PA1 (d) at least one air/fuel nozzle which is provided in the side of the lance outer shell at the downstream end of the fuel lance and through which air can flow out of the air passage into the combustion chamber surrounding the fuel lance; whereby PA1 (e) arranged in the gas pipe, there is at least one gas nozzle through which gas can flow out of the gas passage through the air passage and, with the air, through the at least one air/fuel nozzle into the combustion chamber; and whereby PA1 (f) arranged in the liquid fuel pipe, there is at least one liquid fuel nozzle through which liquid fuel can flow out of the liquid fuel passage through the air passage and, with the air, through the at least one air/fuel nozzle into the combustion chamber.